Survivors of the bloody bomb attacks which struck the Boston Marathon are likely to suffer from post traumatic stress disorder (PTSD), it has been warned.

Bystanders, runners, police and paramedics who were close enough to witness the detonations will be at a higher risk of developing the condition, a leading expert said.

Characterised by nightmares, insomnia, a craving for isolation and fear of crowds, PTSD affects tens of thousands of Iran and Afghanistan veterans mentally scarred by the horrors of war.

Bloody: Bystanders rush to help those injured in the Boston Marathon terror attacks on Monday afternoon. They and other witnesses now face an increased risk of developing post traumatic stress disorder, an expert warns

Dr Harry Croft, a San Antonio-based psychiatrist, who has treated more than 7,000 former soldiers, said the symptoms would be widespread in the immediate aftermath of the attacks.

'If it lasts more than a month, and has enough symptoms, it is then described as PTSD,' he told NBC News.

Initial symptoms often include a sense of disbelief, said Dr Croft, as the experience takes on an almost imaginary aspect. Following that victims either become emotionally numb, or gush with sadness, fear or anger about the horrors they have experienced.

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Typically, PTSD sufferers have recurrent memories of the event. Or they may just block it out entirely.

According to the latest official tally, 183 people were injured and three killed, including one boy of just eight years old, in the terror attack on Monday afternoon.

The latest evidence suggests the bombs used were made from pressure cookers packed with explosives and shrapnel, designed to cause the most grievous injuries possible to those caught up in the blasts.

Disbelief: According to the latest official tally, 183 people were injured and three killed, including one boy of just eight years old, in the terror attack on Monday afternoon

Experts estimate that one-in-five of those who survive or witness sudden, violent incidents like Monday's atrocities will go on to develop PTSD, although the rate can vary widely among civilians and can depend on the severity of the event.

'Long term, the amount of PTSD is greater with man-made traumas as opposed to those caused by hurricanes, floods and fires,' said Dr Croft.

He added that civilians are 'probably' more susceptible than trained soldiers.

Nightmare: Experts estimate that one-in-five of those who survive or witness sudden, violent incidents like Monday's atrocities will go on to develop PTSD, although the rate can vary widely among civilians

Thankfully, after a decade of constant war, experts like Dr Croft have developed keener understanding of the condition and the ways it can be treated.

'We know that for some people intensive debriefing after a trauma does not help, and may worsen symptoms in the long run,' he said.

'But getting survivors to safety, helping them understand what has happened, helping them talk — or be quiet but around others — may be of great value.'

Aside from talking therapies, PTSD sufferers are are commonly treated with drugs including including antipsychotics, antidepressants, anti-anxiety medications.

However, there is currently no specific treatment for PTSD and related disorders.

The high suicide rate among former soldiers is often blamed on the condition.